Advancements in semiconductor technology have lead to the production of large scale integrated circuits (e.g., chips) which have brought about a revolution in the electronics industry. Packaged and unpackaged semiconductor dice and associated micro-circuitry are now widely used in the production of a variety of electronic devices (e.g., portable computers, calculators, watches, cordless telephones, radios, tape recorders, security systems, etc.). As the development of such portable electronic devices continues, a need has arisen for advancements in the technology relating to forming and packaging devices which employ micro-circuitry.
One of the problems associated with conventional micro-circuitry is that the components typically are mounted on a rigid substrate such as a printed circuit board. This substrate must be such that its structural integrity is sufficient to support the weight of the components and to protect the components from damage. The resulting structural rigidity is often a detriment. Some applications require some flexibility in the substrate to accommodate odd configurations or to avoid breaking of the substrate upon impact with other objects.
To allow the miniaturization to advance while providing sufficient support and flexibility, enclosed micro-circuits have evolved. In the past, these enclosed micro-circuits were sometimes manufactured using a flexible substrate, for example, polyester. A conductive trace was formed on the substrate and various electronic components were then attached to substrate in electrical communication with the conductive trace to form the micro-circuit. The micro-circuit was enclosed by bonding a second polyester sheet over the top of the circuitry. In this configuration, the micro-circuitry was enclosed by a flexible polyester sheet on either side of the micro-circuit.
The method of manufacturing the micro-circuit by enclosing it within two polyester sheets has been somewhat successful. On the other hand, if the components of the circuit are too large, this method of manufacture does not function satisfactorily. Specifically, in the situation where components are more than 1.0 mm tall, the top, and sometimes both the top and bottom sheet, had to stretch over or around the oversized component. The unequal stretching of the top and bottom sheets resulted in wrinkles in the sheets and misalignment between the sheets. Both the wrinkles and the misalignment are unacceptable.
The unacceptable nature of this design was especially apparent where components approached 2.5 mm or more in thickness. Examples of larger components would be batteries which are often necessary for a self-contained electrical circuit. Likewise, this enclosed micro-circuit failed where components had variable heights and outside configurations. As was the case with individually excessive heights, the unequal heights and unequal configurations resulted in stretching, bunching and misalignment. When manufacturers attempted to build arrays of enclosed micro-circuits, they found that the stretching, bunching and misaligning problems were additive and necessitated even thinner components and more equally spaced and sized components to fall within acceptable production limits.
For some applications, a rugged, completely self-contained micro-circuit capable of receiving information, storing information and transmitting information, without physical connection to other components is necessary. The previously described enclosed circuit design was not able to accommodate this need.
In view of the deficiencies in the prior art, the present invention is directed to an improved micro-circuit design that allows the circuit components to be enclosed in a flexible package. Accordingly, it is an object of the present invention to provide an improved micro-circuit and method of manufacture.
It is a further object of the present invention to provide an enclosed micro-circuit that is inexpensive and easy to manufacture, yet offers a high degree of reliability while minimizing the possibility of damage to the internal components.
It is yet another object of the present invention to provide a micro-circuit that is enclosed using a flexible substrate and an encapsulant that entirely surrounds the components, yet still allows a relatively high degree of flexibility.
It is a still further object of the present invention to provide a micro-circuit that can be manufactured in multiple units and then singulated into individual micro-circuits.
It is a still further object of the present invention to provide a self-contained, enclosed micro-circuit able to receive information, store the information in a memory and transmit information as required.
Other objects, advantages and capabilities of the present invention will become more apparent as the description proceeds.